1. Field of the Invention
The present invention relates to an imaging device installed at a fixed position and performs imaging of a subject regardless of day and night, an image processing method and a program for the imaging device.
2. Description of the Related Art
In recent years, surveillance cameras (imaging devices) installed at fixed positions (fixed points) in public facilities, commercial facilities, residential areas, or the like to perform imaging of a subject regardless of day and night are widely used. In such a surveillance camera for day and night (also referred to as a day and night function), it is normal to capture a visible light image of a subject during daytime (day) and capture a near-infrared light image of the subject during nighttime.
JP2009-010675A describes a hybrid camera including a visible light camera that captures a visible light image of a subject, and an infrared camera that captures a thermal image of a subject. By applying the hybrid camera of JP2009-010675A to the surveillance camera to provide two types of imaging units to the surveillance camera, it is possible to capture a visible light image during daytime and a near-infrared light image during nighttime.
Further, the hybrid camera of JP2009-010675A generates background image data corresponding to a background region of the subject on the basis of image data of the visible light image, generates moving body image data corresponding to a moving body within the subject on the basis of image data of a thermal image, and generates combination image data obtained by combining the background image data with the moving body image data. Thus, by superimposing the moving body image based on a thermal image on the background image based on the visible light image, it is possible to provide an easy-to-view image.
JP2011-128238A discloses an imaging device that captures a visible light image of a subject through an optical system in which an infrared ray cut filter is inserted into an imaging optical path and captures a near-infrared light image of the subject through the optical system in which the infrared ray cut filter is retracted from the imaging optical path. By applying the imaging device in JP2011-128238A to the above-described surveillance camera for daytime and nighttime, capturing a visible light image during daytime and capturing a near-infrared light image during nighttime can be performed.
In this case, since an optical path length is changed according to the presence or absence of the infrared ray cut filter, a focal length is also greatly changed and image blur may be caused. Therefore, in the imaging device described in JP2011-128238A, a phase modulation element is provided in the above-described imaging optical path to suppress occurrence of image blur.